1. Field of Invention:
The present invention relates to nuclear techniques for measuring oil and water cuts in a multiphase flowstream in petroleum refining and producing operations.
2. Description of Prior Art:
U.S. Patent Application Ser. No. 748,072 relates to a new and improved method and apparatus for determining the presence of salt water in a fluid conduit, such as crude oil at a wellhead, loading dock or other location, or refined product, feed stock or waste water to dispose of at a refinery.
With this technique, the fluid is bombarded with fast neutrons from a neutron source which are slowed down and thereafter engage in thermal neutron capture reactions with materials in the fluid, giving rise to thermal neutron capture gamma rays. The energy spectra of the thermal neutron capture gamma rays are obtained, from which a measure of the relative pressence of chlorine in the fluid may be ascertained, so that if the salinity of the fluid is known, the relative presence of salt water can accordingly be determined. Further, the relative pressure of sulfur may be determined simultaneously with the relative presence of chlorine.
In certain applications, however, it has been found that this technique has limits. For example, it has been found that where the water cut becomes significant, the difference in hydrogen index between the two liquid phases is no longer small relative to that between the gas and liquids, introducing errors in hydrogen normalization. Additionally, if chlorine concentrations increase above very low levels, degraded chlorine gamma rays interfere with gamma ray counts in the hydrogen energy window, and decrease the accuracy of the measurements obtained.